Can Existing Schools Get to High Performance? An Update on School Modernization Strategies

Signs are that funding and community interests may be shifting toward modernizing existing schools instead of building new ones. Old school, meet high performance.
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Sponsored by Pella Commercial and SAFTI FIRST
Layne Evans

Fear Factor: Replacing Unsafe Wired Glass

Discussions of improvements for a school building's performance tend to focus, quite rightly, on the positive opportunities for better resource efficiency and better environments for learning, but in some cases the improvements are not just to improve life inside the school but quite possibly to save it.

It's easy to overlook (see right through?) how much glass is used inside the school building. Vision panels, sidelights, doors, corridors lined with interior windows, even atria and cafeterias - students and teachers inside a school are surrounded by glass. So it is an alarming fact that much of that glass is still a basic type of wired glass that has been used extensively in schools for decades. Wired glass was favored for its fire rating, and was actually considered stronger than regular glass, its superiority so taken for granted that codes made special exemptions for the low impact resistance of wired glass.

Unfortunately, in reality wired glass is about half as strong as a single pane of ordinary glass. The wire acts as a break plane for the tiniest nick or flaw in the glass, giving wired glass less strength than picture frame glass. But it's not just the weakness of the glass that presents a critical safety problem, it's the hazard posed by the wire, which tends to "trap" objects that break through it - including human hands and feet - and make them almost impossible to withdraw without injury. Injuries can be severe and debilitating, and they continue to occur, an estimated 2,300 a year attributed to unsafe wired glass in schools.

In yet another measure of how long it can take schools to make even the most urgent improvements, the federal Consumer Product Safety Commission (CPSC) restricted the use of wired glass that fails to meet human impact standards in all doors and associated windows in 1976. Traditional wired glass doesn't come close to meeting those standards, and it was banned in all building types in 2004 yet it still is present in many school buildings around the country.

The need to replace this glass in schools, where every day children are jostling, kicking, pushing and generally being children, is an obvious and urgent "no brainer."

However, the need for the brain is still there, with thoughtful consideration necessary to ensure that the wired glass is not replaced with something only marginally better. New glass technology exists that protects fully against the basic dangers posed by interior glass: fire and impact. Only one glass will be installed, but it must do both jobs effectively.

In addition, the newer glass products are so effective that they can be used in large expanses, unlike the old wired glass, limited to an area of 9 square feet because of its low impact resistance, or even like many current fire "protective" glass products, limited to smaller areas because of their lack of resistance to radiant heat. The more glass that can be used - now, safely - the more design flexibility there is for bringing in the abundant natural daylight so essential to high performance in schools.

But, before being beautiful, the glass has to be safe, and the key issues are fire and impact.

Fire Resistive or Protective? Discussions of this extremely important distinction in interior glass products can be difficult for designers to present to decision makers. In layman's terms, what we're all looking for is fire protection. The fact that a glass product that is heat "protective" could actually be less protective than one that is heat "resistive" at first appears to be a bit of a tongue twister.

But in terms of fire ratings, "resistive" and "protective" are very specific technical terms, and in an emergency situation, the difference could save children, teachers and others from severe injury or even death.

In the simplest terms, the difference is protection from radiant heat.

Fire ratings are expressed in terms of minutes, 20 minutes, 45 minutes, etc., the time in fire testing that the product was able to withstand heat and/or flames. In general, fire protective assemblies are fire rated from 20-45 minutes and block the immediate spread of smoke and flames. They do not protect against the intense radiant heat passing through the glass. This presents an "invisible" and lethal danger.

A corridor, for example, may be free of flames and thus look "safe," especially to a group of panicked people. But well before 45 minutes, the radiant heat could be so intense that it can cause spontaneous combustion and be more than enough to cause severe burns. Even if people are stopped by the heat before they get far enough to cause injury, that can prevent them from reaching exits, if egress is not completely protected. Heat radiating from the fire can set curtains, clothing - even flammable adhesives in laminated building materials - on fire within minutes. This is why the use of fire protective glass is limited to 20-45 minute applications and 25 percent of wall area. There are door applications that allow the use of 60-90 minute fire protective glass in the vision area, but its size is limited to 100 square inches.

Fire resistive assemblies, on the other hand, can withstand smoke and flames and radiant heat for up to 2 hours. Fire resistive glazing is tested in accordance with ASTM E 119 or NFPA 251 (Standard Method of Tests of Fire Endurance of Building Construction and Materials), which limits the temperature rise on the non-fire side to less than 250 degrees F. above ambient. Because of this ability to limit the passage of radiant heat, fire resistive glazing does not have the 25 percent wall area limitation that fire protective glazing has. When combined with equally rated framing systems, designers have the freedom to create wall-to-wall and floor-to-ceiling glazing applications while still meeting the fire and safety requirements of the code.

"Protective" and "Resistive" are important technical terms that can have critical importance in an emergency.

Graphic: SAFTI FIRST

In an educational facility, where safety is at a premium, fire resistive glazing provides the most protection against all effects of fire.

 

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Originally published in June 2010

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